Arthropods and Echinoderms

Arthropods and EchinodermsMs. Moore2/15/13

Introduction to the ArthropodsPhylum: Arthropoda

What is an Arthropod?Arthropods have a segmented body, a tough exoskeleton, and jointed appendages

Exoskeleton: tough external covering; like a suit of armor that supports and protects the body

Chitin: carbohydrate that makes up exoskeleton

Appendages: structures that extend from the body wallAntennae or legs

Evolution of Arthropods1st arthropods appeared in the sea more than 600 m.y.a.

Natural selectionfewer body segments and highly specialized appendages for feeding, movement, etc.

At least 75,000 species have been identified

Form and Function in ArthropodsFeedingInclude herbivores, carnivores, omnivores, bloodsuckers, filter feeders, scavengers, and parasites.Mouth parts range depending on diet

4Respiration of Terrestrial ArthropodsTracheal tubes: network of tubes that extend throughout the bodySpiracles: small openings along the side of the body attached to tracheal tubesBook lungs: organs that have layers of respiratory tissue stacked like the pages of a book

Respiration of Aquatic ArthropodsFeatherlike gills

CirculationOpen circulatory system

ExcretionMalpighian tubules: saclike organs that extract wastes from blood and add to fecesDiffusion occurs in aquatic arthropods.

ResponseWell developed nervous system, brain, ventral nerve cord, and sense organs (compound eyes).

MovementUse well-developed groups of muscles that are coordinated and controlled by nervous systemFlex or extend muscles

ReproductionTerrestrial: internal fertilization; males have reproductive organ or sperm packetAquatic: internal or external fertilization

Growth and Development in ArthropodsExoskeleton does not grow with the animal. When they outgrow their exoskeletons, arthropods undergo periods of molting

Molting: arthropod sheds its entire exoskeleton and manufactures a larger one to take its place; controlled by the endocrine system (hormones)

Groups of ArthropodsArthropods are classified based on the number and structure of their body segments and appendagesparticularly their mouthparts.

3 Groups:CrustaceansSpiders and relativesInsects and relatives

CrustaceansSubphylum: Crustacea

Primarily aquatic

Crustaceans typically have two pairs of antennae, two or three body sections, and chewing mouthparts called mandibles.

Crustacean Body PlanCephalothorax: formed by fusion of the head with thoraxThorax: lies just behind the head and houses internal organsAbdomen: posterior part of the bodyCarapace: part of exoskeleton that covers cephalothorax

Mandible: mouthpart adapted for biting and grinding foodGills are attached to appendages associated with cephalothoraxDecapods have five pairs of legs.Chelipeds: first pair of legs; bear large claws Swimmerets: flipper like appendages used for swimmingFinal abdominal segment is fused = tail.

P. 721 drawing

Other examples Crustaceans include: CrabsShrimpsLobstersCrayfishesBarnacles (sessile)

How are these alike and different?

Spiders and relativesSubphylum: Chelicerata

Chelicerates have mouthparts called chelicerae and two body sections, nearly all have four pair of walking legs.

Lack antennae found on most arthropods.

Cephalothorax: brain, eyes, mouth, legs

Abdomen: internal organs

Chelicerates have two pairs of appendages attached near the mouthChelicerae: contain fangs used to stab and paralyze preyPedipalps: longer than chelicerae, modified to grab preyUse book gills or book lungs2 classes:Merostomata: horseshoe crabsArachnida: spiders, mites, ticks, scorpions

Horseshoe Crabsamong oldest living arthropods, appeared more than 500 m.y.a.Heavily armored like crabs, but have anatomy closer to spidersSpidersLargest group of arachnidsNo jawsmust liquefy food to swallowChelicerae inject venom paralyze prey inject digestive enzymes stomach breaks downSpinnerets: organs that contain silk glands P722 drawing

Mites and TicksSmall arachnidsOften parasiticChelicerae and pedipalps specialized for digging into hosts tissues and sucking out blood/plant fluidsCephalothorax may stay in skin if pulled out

ScorpionsPedipalps enlarged into clawsAbdomen carries a venomous stinger that can kill or paralyze preyUnlike spiders, scorpions chew prey using chelicerae

Insects and relativesSubphylum: Uniramia

Uniramians have jaws, one pair of antennae, and unbranched appendages.

Centipedes:Class: ChilopoidaSegmented; each segment = one pair of legs, up to 100 pairs Carnivores: mouthparts with venomous claws

Millipedes:Class: DiplopodaHighly segmented; each segment = 2 pairs of legsFeed on dead and decaying plant materialTimid and roll into ball for protection

InsectsWhat is an Insect?Insects have a body divided into 3 partshead, thorax, and abdomen. 3 pairs of legs are attached to thorax.Typical insect also has: pair of antennae, pair of compound eyes, two pairs of wings on thorax, and tracheal tubes.

The class, Insecta, contains more species than any other groups of animals.

Greatest Impact on the World?Responses to StimuliUse sense organs to detect external stimuli

Compound eyes: made of many lenses that detect changes in color and movement

Chemical receptors for taste on mouth, legs, and antennae

Sensory hairs on legs

Ears can be found in odd places (behind legs)Feeding AdaptationsInsects have 3 pair of appendages used as mouthparts:Mandibles used to saw and grind food (ant)Tubelike mouthpart use to suck nectar (moth)Spongelike mouthpart used to lap up food (fly)

Some produce saliva containing digestive enzymes to help break down food (nectarhoney)

Movement and Flight3 pairs of legs can be used for walking, jumping, or capturing and holding prey.

Flighttwo pairs of wings made of chitin (also makes up exoskeleton)

Colonize a wide variety of habitats.Growth and Development:MetamorphosisMetamorphosis: process of changing shape and formIncomplete Metamorphosis: immature forms that undergo gradual change, look very much like adultsNymphs: immature forms; lack functional sex organs and other features like wings; molt several times and grow to acquire adult structuresComplete Metamorphosis: hatch into larvae that look and act nothing like parents; also feed completely different Pupa: stage in which an insect changes from larva to adult; body completely remodeled inside and outP729 stages and 3 examples of insects in eachInsects and HumansNegative effectsTermites destroy wood structuresMoths eat clothing and carpetsBees and wasps produce painful stings

Positive effectsPollination: 1/3 food we eat is pollinated by insectsProducts: silk, wax, honeyInsect CommunicationVisual CuesFireflies: light producing organ produces series of flashes

Chemical SignalsPheromones: specific chemical messengers that affect behavior or development of other individualsFx: to signal alarm or alert; mating

Insect SocietiesSociety: group of closely related animals of the same species that work together for the benefit of the whole group (more than 7 million individuals)

Castes: specialized individuals/body form to perform particular tasksReproductive females that lay eggs called queensReproductive malesWorkers

Communication in SocietiesEach species has its own language of visual, touch, sound, and chemical signals

Bees use a form of dance for communicationRound dance: food is nearby to hiveWaggle dance: food is farther away from hiveAlso shows direction of foodWhat have we learned?Recap

Give an example of 5 different insects and a specialized function/body part of each.EchinodermsEchino- means spiny and dermis means skinEndoskeleton: internal skeleton formed from hardened plates of calcium carbonateEchinoderms are characterized by:spiny skinan internal skeletona water vascular systemsuction-cuplike structures called tube feetMost adults exhibit five-part radial symmetry. Only live in the sea

Form and Function in EchinodermsWater vascular system: internal tube system; filled with fluid; carries out respiration, circulation, and movement

Madreporite: openings to outside fromIn sea stars, this connects to a ring canal that forms a circle around the mouth five radial canals extend from this point

Tube foot: suction cup100s attached to each radial canal

p. 735

FunctionsFeedingScrape algae from rocksTube feet to capture/open preySea stars feed on mollusks open shell and pours enzymes that partially digests mollusk pulls in stomach and prey to mouth

Respiration and CirculationThin-walled tissue of tube feetWater-vascular system

ExcretionDigestive waste anusNitrogenous waste ammonia through skin and gills

ResponseHighly developed nervous system: nerve ring and radial nervesScattered sensory cells

MovementTube feetDetermined by endoskeleton

ReproductionExternal fertilizationLarvae have bilateral symmetry

Groups of EchinodermsSea Urchins and Sand DollarsLarge solid plates that form a box around internal organsDetritivores or grazers that eat algae

Brittle Stars Slender, flexible armsCan shed arms if under attackFilter feeders or detritivores

Sea CucumbersLook like moving picklesTravel in herdsDetritus feeders suck up matter on sea floor

Sea Stars CarnivorousIncredible healing powersEach piece grows into new star

Sea Lilies and Feather StarsFilter feedersOldest class of echinodermsAttached to ocean bottom or atop coral reefs

Ecology of EchinodermsMarine habitatsPopulation controlCrown-of-Thorns: feeds on coral